JP2000045191A - Single wire steel cord and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single wire steel cord having high durability, capable of expressing a good riding comfort and capable of realizing the lightening of a tire, and to provide a method for producing the single wire steel cord. SOLUTION: This single wire steel cord 2 is obtained by flattening a round wire to form two faced flat surfaces and two faced roundly curved surfaces. Therein, the DEW flatness ratio of the minor diameter D of the cord to its major diameter W is 0.50 to 0.95, and the cord is waved at least toward the minor diameter. The steel cord 2 is embedded in the belt portion of a tire so that one of the flat surfaces is directed to the ground plane side of the tire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-wire steel cord used for reinforcing various types of vehicle tires and a method for manufacturing the same, and more particularly to a single-wire steel cord used by being embedded in a tire belt and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, as a part of the promotion of global warming prevention, strict regulations on total exhaust gas have spurred the improvement of fuel efficiency of automobiles, and it has been attempted to reduce the thickness of rubber parts for the purpose of reducing tire weight. The movement to do is becoming active.
For this reason, great expectations have been placed on the development of steel cords as tire reinforcing materials from the automobile industry. In the future, from the perspective of improving the global environment, there is an urgent need to develop thinner and lighter tires and develop single-wire steel cords that emphasize tire performance when driving, especially cornering power and ride comfort. I have.

A belt layer of a radial tire for a passenger car is provided between a tread and a carcass, and has a function of increasing the rigidity of the tread by strongly tightening the carcass like a tag as a belt stretched in a circumferential direction. . The function of the belt layer is indispensable for the tire to support the vehicle weight, and also has a role of exerting the power in cornering.

[0004] A steel cord having a 1 x n structure in which a plurality of wires are twisted is generally used for a tire belt layer. The steel cord having such a stranded wire structure has high rigidity, but on the other hand, on a non-paved road having an uneven road surface, the resilience of the tire becomes too strong, and the riding comfort is not good. In addition, a crack is easily generated on the tread surface, and rainwater or the like enters the inside of the tire from the crack, and the cord wire is corroded at an early stage. Further, when the tire is deformed or vibrated, the twisted wires rub against each other, causing so-called fretting wear, and there is a problem that the cord wire is significantly deteriorated by fatigue.

In order to solve these problems, it has been proposed to use a single-wire steel cord made of a round wire as a tire belt layer in place of a stranded wire steel cord. This is because the single-wire steel cord is more flexible than the stranded wire steel cord.

However, conventional single-wire steel cords having a round wire structure and steel cords having a stranded (1 × n) structure have the following problems.

[0007] The characteristics used to evaluate the performance of a steel cord include two characteristics: "kill" and "arc height".
One is given. "Kill" is one of the code characteristics used for evaluating the rotational torque inherent in the code itself.
"Arc height" is one of the cord characteristics used for evaluating the linearity of a steel cord. If the kill is uneven or uneven, or if the arc height is too large, the calendering process of the tire manufacturing process (Steel cords are laid out on a thin rubber sheet, and another thin rubber sheet is placed on this This is because in the step of sandwiching the steel cord into the sheet), defects such as twisting and swelling occur in the calendar sheet.

However, the conventional stranded wire structure (1 ×
In the case of the cord n) and the cord of a single round wire, the kill and the arc height are apt to fluctuate due to a material factor of the wire or a mechanical factor such as a wire drawing machine or a twist wire machine. In particular, because kills vary greatly, each product is currently inspected even at a general quality assurance level.

() Kill As the performance of a steel cord used for a tire, it is particularly important to evaluate the rotational torque of the steel cord, that is, the rotational torque (kill) inherent in the cord itself. Hereinafter, the kill will be described with reference to FIG.

The method of measuring the kill is as shown in FIG. 1 with the cord end 2c of the finished spool 1 folded into an L shape and fixed to a fixture (not shown) as shown in FIG.
6m) from the spool 1 and then the cord terminal 2c is released from the fixture and the number of rotations of the cord 2 is counted. In the case of a normal S twist, a plus-skill (+) is defined as a rotation in the same direction (clockwise) as the twist direction, and a minus kill (-) as a rotation in the opposite direction (counter-clockwise) of the twist direction. I do. Generally, the kill is good if the number of revolutions is less than two revolutions, and it can be said that the code is practically acceptable.

() Arc Height Evaluation of the linearity (arc height) of a cord in an unconstrained state is important as the performance of a steel cord used in a tire belt portion. Hereinafter, the arc height will be described with reference to FIG.

The length L2 (= 400 m) shown in FIG.
As shown in FIG. 2B, the height AH of the arc formed by the cord 2 corresponds to the arc height when the cord 2 cut in m) is in contact with the flat plate 3 at both ends as shown in FIG. Usually, if the arc height AH is within 30 mm, it is good, and it can be said that the cord has no practical problem.

(1) Cornering Power and Ride Comfort One of the performances required of a steel radial tire is that the steering wheel is good at high speed running, that is, the cornering power for avoiding danger is large. Conventionally, cords with high rigidity have been used, but the tires receive up-and-down vibrations on unevenness of the non-paved road surface, so that riding comfort is reduced. Thus, the performance required for the steel cord for reinforcing the tire belt layer in the future is two, that is, the durability in the lateral direction at the time of cornering and the good riding comfort at the time of running. Combining these two performances is important for future steel cords.

() Reducing Tire Rubber In recent years, automobiles have tended to design fuel-efficient vehicles with an emphasis on measures to prevent global warming. Have been. However, conventional stranded wire cords and round wire single-wire cords have a limit in improving the tire rubber thickness.

[0015]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a single-wire steel cord which has a large cornering power, is excellent in ride comfort, and can realize thickening of tire rubber, and a method of manufacturing the same. It is in.

In order to increase the lateral durability during cornering, it is important to use a cord having high lateral rigidity (in-plane bending rigidity) E1. In addition, in order to improve the ride comfort, the rigidity in the vertical direction (out-of-plane bending rigidity) E2 is moderate in order to flexibly receive the unevenness of the tire contact surface and reduce the rattled ride comfort that the rider feels. It is advantageous to use a strong code.

In order for the steel cord of the belt portion to have both high durability and flexibility, the in-plane bending rigidity E1 is larger than the out-of-plane bending rigidity E2 (E1> E2), and the rigidity has anisotropy. It is important.

However, in the case of a conventional stranded wire structure cord or a round wire single wire cord, two-dimensional shaping (gear crimping) is used.
This is because there is almost no difference between the stiffness E1 in the horizontal direction and the stiffness E2 in the vertical direction even if a three-dimensional shaping (spiral) is applied. For this reason, it is not possible to simultaneously satisfy both the lateral durability and the vertical ride comfort during cornering. In other words, if the emphasis is placed on the endurance, the ride comfort is degraded, while if the emphasis is placed on the ride comfort, the endurance cannot be obtained.

Incidentally, it has been proposed to use a single-wire steel cord as disclosed in Japanese Patent Application Laid-Open No. 7-1915 for a tire belt layer instead of a single-wire steel cord made of a round wire. Such a single-wire steel cord flattens the wire, for example, as disclosed in Japanese Unexamined Patent Publication No. 10-25680.
It is a two-dimensional corrugated process using the device described in the official gazette, and has excellent adhesiveness with rubber, and high bending rigidity, so it is excellent to use this for the belt portion of a passenger car tire. Steering stability is obtained. However, this single-wire steel cord is insufficient for reducing the thickness of tire rubber, and it cannot be said that riding comfort is necessarily improved.

[0020]

The inventors of the present invention have made intensive studies for reducing the thickness and weight of the tire and improving the performance thereof, and as a result, have completed the present invention described below.

The single-wire steel cord according to the present invention has two flat surfaces opposed to each other by flattening a round wire.
A single wire steel cord having two round curved surfaces, wherein an aspect ratio D / W of a minor axis D to a major axis W is 0.5 to 0.95.
And is corrugated at least in the minor axis direction,
It is used by being embedded in a tire belt portion so that one flat surface faces the tire tread surface side.

The method for manufacturing a single-wire steel cord according to the present invention is a method for manufacturing a single-wire steel cord used by being embedded in a tire belt portion such that one flat surface faces the tire contact surface side, and (a) Flattening the round wire so that the flatness ratio D / W between the short diameter D and the long diameter W is in the range of 0.50 to 0.95; and (b) the flattened flattened in the step (a). Corrugating the wire in the minor diameter direction.

Further, it is preferable that before the step (a), there is provided a long diameter corrugating step of corrugating the round wire in a direction orthogonal to the corrugating direction in the short diameter corrugating step (b). In this case, it is desirable that the aspect ratio D / W is in the range of 0.80 to 0.95 in the step (a).

In the case of a single-wire steel cord (cord of type 1) which is crimped only in the short diameter direction, the flatness ratio D1 /
It is preferable that W1 be in the range of 0.50 to 0.95.

The reason why the upper limit of the aspect ratio D1 / W1 is set to 0.95 is that if the wire exceeds 0.95 and becomes close to a perfect circle, the effect of reducing the kill (rotation torque) by rolling cannot be seen. Also, there is no difference in rigidity between the major axis direction and the minor axis direction.

On the other hand, the lower limit of the aspect ratio D1 / W1 is 0.5
The reason why it was set to 0 is that a wire drawn as a wire for a steel cord using 0.82% high carbon steel was 3%.
This is because the wire after rolling has a high tensile strength of about 00 kgf / mm ^2, and may have cracks in the wire after rolling when a high flattening ratio of less than 0.50 is performed.

The maximum value of the corrugated height F1 in the minor diameter direction is 0.
Preferably, it is 3 mm. If the corrugated height F1 is excessively increased beyond this, the rubber portion becomes thick and deviates from the purpose of reducing the weight of the tire.

On the other hand, the minimum value of the corrugated height F1 in the minor diameter direction is preferably 0.05 mm. Arc Height H
Is required to be corrugated to a height of at least 0.05 mm in order to reduce the diameter to within 30 mm (pass judgment).

It is desirable that the corrugation pitch P1 is 2 to 20 mm. This is because this range is a practical corrugated pitch.

Here, "corrugation" refers to forming a wire into a two-dimensional or three-dimensional shape by applying a stress greater than the elastic limit to the wire.

The “crimp corrugation” here means 1
Forming a wire into a two-dimensional shape that repeats the same wave in two planes. A typical example of the crimping is a gear crimping process in which a wire is inserted between a pair of gears to form the wire. The crimping includes a process of crushing a three-dimensional spiral wire from the side to form a two-dimensional shape.

[0032] Here, the term "arcing" refers to shaping a wire into a two-dimensional shape consisting only of a combination of smoothly continuous curves that do not include a linear portion in one plane. As a typical example of the arc corrugation, there is a pin roller corrugation process in which a wire is bitten between a pair of pin rollers.

Since the cord set only in the short diameter direction (cord of type 1) has a comparatively low elongation setting area,
If elongation that cannot be covered by type 1 is required, a cord (type 2 cord) corrugated in both directions with a high elongation setting area is used.

Flatness ratio D2 / W2 of type 2 cord
((D2; short diameter of flat wire) / (W2; long diameter of flat wire)) is preferably in the range of 0.80 to 0.95. The reason why the upper limit of the aspect ratio is set to 0.95 is that if the aspect ratio exceeds 0.95 and the wire becomes close to a perfect circle, the effect of reducing the kill (rotation torque) by rolling is not observed, and the major axis This is because there is no difference in rigidity between the direction and the minor diameter direction. Further, the reason why the lower limit of the aspect ratio is set to 0.80 is that, in the case of the type 2 cord, after the wire is drawn, three processes of the long diameter crimping, the drive roll rolling, and the short diameter crimping are performed. This is to prevent a reduction in strength due to damage to the wire during rolling.

In the type 2 cord, the maximum value of the crimp wave height F3 in the short diameter direction is 0.3 mm, and the crimp wave height F2 in the long diameter direction is in the range of 0.05 to 0.5 mm. Is preferred. Corrugation processing height F in the minor axis direction
The reason why the maximum value of 3 is set to 0.3 mm is that if the corrugated height is too high, the rubber of the tire becomes thick and deviates from the purpose of weight reduction. The reason why the maximum value of the corrugated processing height F2 in the major diameter direction is 0.5 mm is that if the corrugated height is too large, the elongation of the cord becomes too large, and depending on the arrangement of the cords, This is because peaks and valleys face each other, and irregularities in gaps between cords become remarkable, which is not preferable. The reason for setting the minimum value of the corrugated processing height F2 in the major axis direction to 0.05 mm is as follows.
If the corrugation height is made smaller than this, the arc height becomes 3
This is because it cannot be reduced to within 0 mm (pass judgment).

The corrugated pitches P2 and P3 are desirably 2 to 20 mm in both the major axis direction and the minor axis direction.
This is because this range is a practical corrugated pitch.
However, the set length of the corrugated pitch is such that the pitch length P2 in the major axis direction is positive with respect to the pitch length P3 in the minor axis direction in order to eliminate the non-uniformity of the pitch between the major axis direction and the minor axis direction. Set several times.

The constituent wire has a tensile strength of 300.
It is desirable to use a high-tensile steel wire ~380kgf / mm ² class. This is because the tensile strength of the wire needs to be 280 kgf / mm ² or more in order for the single wire steel cord to obtain a desired breaking strength. On the other hand, if the tensile strength of the wire exceeds 400 kgf / mm ² , the wire becomes brittle and the wire is easily broken.

The constituent wire has a carbon content of 0.7.
It is desirable to use a high-strength steel wire of 5 to 0.95% by weight. This is because the carbon content of the wire needs to be 0.7% by weight or more in order for the single wire steel cord to obtain a desired breaking strength. On the other hand, if the carbon content of the wire exceeds 1.0% by weight, the wire becomes brittle and the wire is likely to break.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

Using the manufacturing method shown in FIGS. 3 and 4A, FIGS. 4B and 4C and FIGS.
A type 1 single-wire steel cord 2A shown in FIG. 11 (b) is manufactured, and using this single-wire steel cord 2A, FIG.
(C) of the steel radial tire 10A was manufactured. 13 (b) and 13 (c) and FIGS. 14 (a) and 14 (b) using the manufacturing process shown in FIGS. 12 and 13 (a).
A single-wire steel cord 2B of type 2 shown in FIG. 14 (b) is manufactured, and the single-wire steel cord 2B is used to manufacture the single-wire steel cord 2B shown in FIG.
(C) of the steel radial tire 10B was manufactured.

Hereinafter, each will be described in detail.

(Examples 1 and 2; Type 1 cord) A steel wire having a carbon content of 0.82 ± 0.02% by weight was prepared as a strand (step S1). Put this wire in a heating furnace for 9
After heating and holding at a temperature of 50 ° C. for 30 seconds, quenching is performed in a fluidized bed furnace using sand for 8 seconds at a temperature of 550 ° C. (step S2), and 63% by weight of Cu and 37% by weight of Zn in an electroplating bath. The surface of the element wire is brass-plated to the composition (step S3), and the plated steel wire is drawn by a wire drawing machine 5 to obtain a high-tensile steel wire 2 having a tensile strength in the range of 308 to 312 kgf / mm ² ( Step S4). The diameter of the drawn wire 2 is 0.40 mm. In addition, 1kg of wire
The amount of brass plating per unit is about 4 g.

Subsequently, the round wire 2 is sent to the driving roll rolling device 7, and the round wire 2 is fed to a pair of upper and lower rolling rolls 71, 71.
0.30mm x 0.46mm crushed by 72
A flat wire 2a of (shorter diameter × longer diameter) size was obtained (step S
5).

The drive roll rolling device (flattening machine) 7 will be described with reference to FIGS. The flattening machine 7 includes a pair of upper and lower caliber rolls 71 and 72. The upper roll 71 is connected to a drive shaft 73 driven to rotate by a motor 78, and the lower roll 72 is connected to a drive shaft 74 driven to rotate by a motor 79. A large gear 76 is attached to the drive shafts 73 and 74, and the large gear 76 meshes with a small gear 77 attached to the rotary drive shaft of each of the motors 78 and 79, respectively. Each roll 7
A predetermined concave shape caliber 71a, 7
2a are respectively formed. Each roll shaft 73, 74
Are brackets 73b, 74 via bearings 73a, 74a.
b. The lower bracket 74b is fixed to a frame (shown) of the rolling device, and the upper bracket 73b
Is connected to the lower bracket 74b by an adjusting screw 75. When the adjustment screw 75 is turned, the upper roll 71 moves up and down together with the upper bracket 73b, and the upper roll 71 and the lower roll 7
The gap between the two is changed. Note that a hydraulic cylinder mechanism may be used instead of the adjusting screw 75 for the roll gap adjusting mechanism.

The round wire 2 is bitten between the calipers 71a, 72a of the upper and lower rolls 71, 72 and is crushed from above and below to form the flat wire 2a. Continue flat wire 2
a is sent to the corrugating machine 8 and the rolls 83a, 8
The flat cord 2A corrugated in one direction by corrugating in the short diameter direction by 3b (step S6).

Referring to FIG. 7 and FIG.
Will be described. A pair of upper and lower large rollers 82a and 82b are housed in a housing 81 of the corrugating machine 8. The housing 81 has an entrance guide 85 and an exit guide 86. The wire 2 is introduced into the housing 81 through the entrance guide 85, and the large rollers 82a, 82b
It passes through the gap and is sent out of the housing 81 via the outlet guide 86.

As shown in FIG. 9, the large rollers 82a, 82
Holders 87a and 87b are provided at equal pitches on the outer circumference of b, and small diameter pin rolls 83a and 83b are attached to the holders 87a and 87b, respectively. The pin roll 83a (83b) and the pin roll 83 adjacent to each other
a (83b) so that there is almost no gap. The upper roller 82a is coaxially connected with the gear 84a, and the lower roller 82b is coaxially connected with the gear 84b. The upper and lower gears 84a and 84b mesh with each other. The upper and lower rollers 82 are driven by both gears 84a and 84b.
a, 82b without causing slip between the upper and lower rollers 82.
a and 82b are surely synchronously rotated.

When the wire 2 is caught between the large rollers 82a and 82b, it is bent by the upper and lower pin rolls 83a and 83b, and smoothly continuous as shown in FIGS. 10 (b), (d) and (f). It is corrugated into an arc shape. In this case, the diameter D of the pin rolls 83a and 83b is the wire diameter d.
It needs to be much larger. In addition, the pin roll 8
It is preferable that the diameter D of the wires 3a and 83b be in the range of 5 to 50 times the wire diameter d.

The wire 2 may be two-dimensionally crimped by using a gear crimping machine disclosed in Japanese Patent Laid-Open No. 10-25680 instead of the above-described arcing machine 8. The appearance of the wire 2K corrugated by such a gear crimping machine is shown in FIGS. 10 (a), (c) and (e).

As shown in Table 1 and FIGS. 11A and 11B, the cords 2A of Examples 1 and 2 (type 1) have a corrugated height F1 of 0.1 mm in the minor diameter direction, respectively. 0.1
mm, short diameter D1 is 0.30 mm, 0.36 mm, long diameter W
1 is 0.46 mm, 0.44 mm, aspect ratio D1 / W1 is 0.65, 0.82, and corrugation pitch P1 is 6 mm, 6 m
m.

Further, the cord 2A was wound around a reel of the winding machine 9, this reel was attached to the supply side of a cutting line, and the cord 2A was cut into a predetermined length by a cutting machine (not shown) (step S7). The length of the cutting cord 2A is 200m
It is. In addition, as shown in Table 1, the kill of the cord 2A was 0 to 0.75 rotation (average 0.5 rotation), and the arc height was 10 to 28 mm (average 15 mm, 24 mm).

Code 2A of Examples 1 and 2 (Type 1)
Is that the rigidity index G2 in the minor axis direction is 74,97, the rigidity index G1 in the major axis direction is 149,114, and the rigidity ratio G1 / G
2 was 2.00, 1.18. The “stiffness index”
Is the ratio when the rigidity G3 of the round wire is set to the reference value of 100, and was measured in each of the two directions shown in FIG. The cord 2A of type 1 has a breaking elongation of 2.5.
It was found to be in the low region of ~ 3.5%.

The so-called calendaring in which the cutting cords 2A were laid in parallel on a raw rubber sheet at predetermined pitch intervals was performed (step S8). In the calendering step S8, the cords 2 are placed such that one flat surface is parallel to the surface of the raw rubber sheet.
Lay A. Since the cutting code 2A has a small arc height, the cutting codes 2A can be easily laid and arranged. The pitch interval of the laying is, for example, 1.2 mm.

The rubber sheet is cut into a predetermined size (step S9). The two cut sheets 12A and 14A are superimposed on the belt portion of the tire-shaped rubber molded product so that the embedded cords 2A cross each other at a predetermined angle. Further, the rubber member 16 having the tread 18 is attached to the outer (second layer) sheet 14A, whereby the cord 2A is completely embedded in the rubber (step S10). The molded article assembled in this manner is heated to a predetermined temperature to be integrated, and FIG.
The tire product 10A shown in FIG. 1 (c) was obtained (step S1).
1).

In such a tire product 10A, the cord 2A is arranged such that the short diameter portions adjacent to the belt layers 12A and 14A are arranged at a constant interval, and are arranged obliquely with respect to the rotation direction of the tire. ing. This structure
The rigidity E1 in the horizontal direction is hardened to increase the durability, and the rigidity E2 in the vertical direction is softened to enable a soft ride.

Next, FIGS. 12 and 13 (a),
A type 2 single-wire steel cord and a method for manufacturing the same will be described with reference to (b) and (c).

(Examples 3 and 4; Type 2 cord) A steel wire having a carbon content of 0.82 ± 0.02% by weight was prepared as a strand (step S21). After heating the wire at a temperature of 950 ° C. for 30 seconds in a heating furnace, the wire is quenched in a fluidized-bed furnace using sand for 8 seconds at a temperature of 550 ° C. (Step S22). The surface of the wire is brass-plated to a composition of 63% by weight of Cu and 37% by weight of Zn (Step S23), and the plated steel wire is drawn by a wire drawing machine 5, and has a tensile strength in the range of 308 to 312 kgf / mm ^2. It was set as the tension steel wire 2 (step S24). The diameter of the drawn wire 2 is 0.40 mm. In addition, wire 1
The amount of brass plating per kg is about 4 g.

Subsequently, the wire 2 is sent to the corrugating machine 8, which is corrugated in the major axis direction by the pin rolls 83a and 83b, and the wire 2b1 is corrugated in one direction.
(Step S25). It should be noted that a gear crimping machine disclosed in Japanese Patent Laid-Open No. 10-25680 may be used in place of the arcing machine 8 described above.

Subsequently, the wire 2b1 is sent to the flattening machine 7, which is crushed from above and below by a pair of rolling rolls 71, 72 to form a flat wire 2b2 having a size of 0.36 mm × 0.44 mm (short diameter × long diameter). (Step S2)
6). The apparatus shown in FIGS. 5 and 6 was used as the flattening machine 7.

Subsequently, the flat wire 2b2 is sent to the corrugating machine 8, and is fed to the pair of pin rolls 83a, 83b.
Thus, a flat cord 2B corrugated in the short diameter direction to obtain a flat cord 2B corrugated in two directions (step S27). It should be noted that a gear crimping machine disclosed in Japanese Patent Laid-Open No. 10-25680 may be used in place of the arcing machine 8 described above.

As shown in Table 1 and FIGS. 14A and 14B, the code 2B of the third and fourth embodiments (type 2)
The corrugated height F2 in the major axis direction is 0.1 mm, 0.
1 mm, the corrugated height F3 in the minor diameter direction is 0.1 mm, 0.1 mm.
1 mm, minor axis D2 is 0.36 mm, 0.38 mm, major axis W2 is 0.44 mm, 0.43 mm, aspect ratio D2 / W2
Are 0.82 and 0.88, the corrugation pitch P2 in the major axis direction is 6.0 mm and 6.0 mm, and the corrugation pitch P3 in the minor axis direction.
Are 3 mm and 3 mm.

Further, the cord 2B was wound on a reel of the winding machine 9, this reel was attached to the supply side of a cutting line, and the cord 2B was cut into a predetermined length by a cutting machine (not shown) (step S28). The length of the cutting cord 2B is 200
m. In addition, as shown in Table 1, the kill of the cord 2B was 0 to 0.75 rotation (average 0.5 rotation), and the arc height was 8 to 20 mm (average 12 mm, 17 mm).

The type 2 cord 2B has a rigidity index G2 of 94,97 in the minor axis direction and a rigidity index G1 of 11 in the major axis direction.
1,109 and the rigidity ratio G1 / G2 were 1.18, 1.12. The “rigidity index” is a ratio when the rigidity G3 of the round wire is set to a reference value of 100, and was measured in two directions shown in FIG. Further, it was found that the type 2 cord 2B had a high elongation at break of 3.0 to 5.0%.

The so-called calendaring in which the cutting cords 2B were laid in parallel at predetermined pitch intervals on a raw rubber sheet was performed (step S29). In this calendaring step S29,
The cords 2B are laid so that one flat surface is parallel to the raw rubber sheet surface. Since the arc height H of the cutting code 2B is small, the cutting codes 2B can be easily laid and arranged. The pitch interval of the laying is, for example, 1.2 mm.

The rubber sheet is cut into a predetermined size (step S30). The two cut sheets 12B and 14B are superimposed on the belt portion of the tire-shaped rubber molded product so that the embedding cords 2B cross each other at a predetermined angle. Further, the rubber member 16 having the tread 18 is attached to the outer (second layer) sheet 14B, whereby the cord 2B is completely embedded in the rubber (step S31). The molded article assembled in this manner is heated to a predetermined temperature and integrated to obtain a tire product 10B shown in FIG. 14C (step S3).
2).

The flatness ratio ((D2: short diameter of flat wire) / (W2: long diameter of flat wire)) of the flat wire cross section applied to Type 2 was 0.80 to 0.95.

The reason why the upper limit of the aspect ratio is set to 0.95 is as follows.
If the aspect ratio exceeds 0.95 and becomes close to a perfect circle, the effect of reducing the kill (rotation torque) by rolling will not be observed, and there will be no difference in rigidity between the major axis direction and the minor axis direction.

The reason why the lower limit of the aspect ratio is 0.80, which is higher than 0.50 of Type 1, is that Type 2 has three types of crimping in the major axis direction + driving roll rolling + minor axis direction after wire drawing. This is because the number of times of crimping is one more than that of type 1 in order to perform the number of times of processing, and the purpose is to prevent a reduction in strength due to damage to the wire in rolling.

The corrugated height in the major axis direction is 0.05 to 0.5.
The range was 5 mm.

The maximum value of the corrugated processing height in the major axis direction is
The reason for setting it to 0.5 mm is that if the corrugated height is too high,
This is because peaks and valleys face each other depending on the extension of the cords and the arrangement of the cords.

The maximum value of the corrugation processing height in the minor diameter direction is
The reason why 0.3 mm is set is that if the corrugated height is too high,
This is because the rubber of the tire becomes thick and deviates from the purpose of weight reduction. The reason why the minimum value is set to 0.05 mm is that the arc height cannot be reduced to a standard of 30 mm or less unless the corrugation in the minor diameter direction is performed at least to this extent.

The type 2 cord described above had good arc heights (linearity) of 12 mm and 17 mm and good quality with a kill (rotation torque) of 0.5 rotation and almost zero.

The tire in which the type 2 is buried can be expected to have the same durability as the type 1 in terms of the durability due to the rigidity in the lateral direction and the soft riding comfort due to the soft rigidity in the longitudinal direction.

Next, FIGS. 15A and 15B and FIG.
The single-wire steel cords of Comparative Examples 1 to 3 will be described with reference to (a) and (b) of FIG.

(Comparative Example 1: Two-dimensional round crimping code for round wire) Using the same wire as that of the above-described embodiment, two-dimensional round wire crimping for the cross section shown in FIGS. 15 (a) and (b) is used. The manufactured single-wire steel cord 2C was manufactured as Comparative Example 1. As shown in Table 1, the code 2C of Comparative Example 1 has a diameter D
Is 0.40 mm and the corrugation pitch P is 6 mm. The rigidity index G2 in the minor axis direction is 100, the rigidity index G1 in the major axis direction is 103, and the rigidity ratio G1 / G2 is 1.03. Further, the arc height (linearity) of the code 2C is 3
9 mm, and the kill (rotation torque) was 1.0 rotation.

Comparative Example 2 Round Wire Three-Dimensional Spiral Processing Code A round wire three-dimensional spiral processing having a cross section shown in FIGS. 16A and 16B was performed using the same wire as that of the above embodiment. Single wire steel cord 2D was manufactured as Comparative Example 2. As shown in Table 1, the code 2D of Comparative Example 2 has a diameter D
Is 0.40 mm and the spiral pitch P is 6 mm.
The rigidity index G2 in the minor axis direction is 100, the rigidity index G1 in the major axis direction is 100, and the rigidity ratio G1 / G2 is 1.00. Further, the arc height (linearity) of the code 2D is 1
8 mm, and the kill (rotation torque) was 0.5 rotation.

Comparative Example 3 Round Wire Cord A single-wire steel cord 2 made of a round wire having a cross section shown in FIG. As shown in Table 1, the round cord 2 of Comparative Example 3 had a diameter D of 0.3.
40 mm. The rigidity index G2 in the minor axis direction is 10
0, rigidity index G1 in the major axis direction is 100, rigidity ratio G1 / G
2 is 1.00. Further, the arc height (linearity) of the round cord 2 is 45 mm, and the kill (rotation torque) is 2.5.
It was a spin.

Each of the above-mentioned type 1 and type 2 cords was manufactured, and the characteristics thereof were examined. As a result, the following effects [] to [] were confirmed.

[] Reduction of Kill (Rotation Torque Inherent in Wire) by Flattening (a) Kill is one of the important performances for assuring the quality of a steel cord. It is especially important to be able to manage the killing on the wire drawing machine when making a single wire steel cord directly on the wire drawing machine. Usually, when the kill is measured for the round wire after drawing, the number of rotations is about 1 to 5 times.

The present inventors have confirmed that the flattening of the round wire reduces the kill to almost zero. By driving roll rolling the wire, the kill is 0
It has become possible to stably produce one low-level single-wire steel cord once, and it has become possible to change the conventional 100% inspection of kills to sampling inspection (periodic management). As a result, the frequency of inspections has been drastically reduced and the work has been greatly reduced, and it has become possible to produce cords with more stable killing than ever.

(B) The flat wire has a rigidity G in the major axis direction.
1 shows anisotropy of rigidity in which the rigidity G2 is larger than the rigidity G2 in the minor axis direction. When the rigidity G1 in the major axis direction and the rigidity G2 in the minor axis direction of these flat wires are compared with the rigidity G3 of the conventional round wire, it has been found that the following equation (1) is established.

G1>G3> G2 (1) Since flat cords are arranged on the belt layer of the tire such that the flat cord faces the tire contact surface, the lateral direction of the tire is smaller than that of a conventional round wire. Has a high rigidity E1. As a result, the cornering power is excellent, the longitudinal rigidity E2 of the tire is reduced, and the flexibility of the entire tire is increased, so that the riding comfort is improved.

[] Reduction effect of arc height (wire linearity) by corrugation (a) Flat wire not corrugated has a large arc height and is unsuitable as a cord. The arc height is greatly improved by corrugating in the radial direction, and within the control range of general code (≦ 30 m
m), the arc height could be reduced.

(B) Elongation required by the cord was secured by applying two types of corrugations.

The cord 2A of type 1 is corrugated in the minor diameter direction, and has a breaking elongation in a low range of 2.5 to 3.5%.

The cord 2B of the type 2 is corrugated in the major axis direction and the minor axis direction, and has a breaking elongation of 3.0 to 3.0.
It is in the high region of 5.0%.

[] Thinning By arranging the corrugated flat single-wire cord so that the flat surface faces the tire contact surface side, the rubber thickness is reduced as compared with the conventional single wire cord made of round wire or 1 × n stranded wire cord. The thickness has been reduced, making it possible to reduce the weight of the tire.

[] Cost reduction The wire drawing machine, which is a process prior to the stranded wire process, does not use a stranded wire machine at all, and is provided with a flattening machine (drive roll rolling machine) and a corrugating machine (pin roll machine or gear crimping machine). ), And flattened rolling and corrugating were continuously performed on the drawn wire, thereby making it possible to manufacture a flat single-wire steel cord. As a result, in addition to eliminating the stranded wire process, the processing speed of the wire drawing machine is approximately three times faster than that of a single wire cord using a conventional stranded wire machine, and it is economically significant. Cost reduction.

[] Evaluation of Fatigue Resistance The fatigue resistance of each single-wire steel cord was evaluated using a belt durability tester 60 shown in FIG. 18 and 19
As shown in the figure, the test piece 90 is
Single wire steel cord 2 (2A, 2B, 2C, 2D)
And a backbone layer in which five stranded wire cords 93 having a 2 + 2 × 0.25 configuration are embedded in a line at equal pitch intervals on the back side of the rubber member 91. is there. Incidentally, the dimensions of each part of the test piece 90 are such that the thickness T is 6 mm, the width W is 12 mm, and the length L4 is 400 mm.
It is.

The belt durability tester 60 has a roller 61 having a diameter of 20 mm. A test piece 90 is wound around the roller 61 so that the sample layer is on the abdominal side (inside).
Weights 62 were attached to both ends, respectively, so that a load of 60 kgf was applied to the test piece 90. Test piece 90
The direction was switched at a cycle of 60 times per minute with a stroke of 50 mm, and this was repeated 2000 times.

After the test was completed, the sample layer of the test piece 90 was irradiated with soft X-rays to take an X-ray transmission photograph. Observing the X-ray radiograph, the number of breaks (NB
R) was counted for each sample. The number of tests was 5 lots as one lot, and the average value was evaluated.

[0092]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining killing of a single-wire steel cord.

2A is a diagram showing a steel cord cut to a predetermined length, and FIG. 2B is a diagram for explaining a method of measuring the arc height of the steel cord.

FIG. 3 is a process chart showing a method for manufacturing a single-wire steel cord according to the first embodiment of the present invention.

4A is a schematic view showing a production line of a single-wire steel cord according to the first embodiment, FIG. 4B is a schematic view showing a single-wire steel cord in each step, and FIG. 4C is a schematic view of a single-wire steel cord in each step. Cross-sectional view.

FIG. 5 is a front view showing a main part of a flattening device (drive roll rolling device).

FIG. 6 is a side view showing a main part of a flattening device (drive roll rolling device).

FIG. 7 is a front view showing an outline of a device with an arc wave (a pin roll processing device).

FIG. 8 is a side view showing an outline of a device with a circular wave (a pin roll processing device).

FIG. 9 is a partially enlarged view showing a main part of an arc wave corrugating device (pin roll processing device).

10A is a schematic view of a gear crimped single-wire steel cord (0.25HT), FIG. 10B is a schematic view of an arc-waved single-wire steel cord (0.25HT),
(C) is a single wire steel cord with a gear crimp wave (0.
30d), (d) is a schematic diagram of a single-wire steel cord with an arc wave (0.30HT), and (e) is a single-wire steel cord with a gear crimp (0.35HT).
(F) is an outline schematic diagram of a single-wire steel cord (0.35HT) with an arc wave.

FIG. 11A is a cross-sectional view of a single-wire steel cord (type 1 cord) of the first embodiment, FIG. 11B is an outline schematic diagram of a single-wire steel cord (type 1 cord) of the first embodiment, (C) is a schematic cross-sectional view of a steel radial tire in which the single-wire steel cord (type 1 cord) of the first embodiment is embedded.

FIG. 12 is a process chart showing a method for manufacturing a single-wire steel cord according to a second embodiment of the present invention.

13A is a schematic view showing a production line of a single-wire steel cord according to a second embodiment, FIG. 13B is a schematic view showing the outline of a single-wire steel cord in each step, and FIG. 13C is a schematic view of a single-wire steel cord in each step. Cross-sectional view.

14A is a cross-sectional view of a single-wire steel cord (cord of type 2) of the second embodiment, FIG. 14B is an outline schematic diagram of a single-wire steel cord (cord of type 2) of the second embodiment, (C) is a schematic cross-sectional view of a steel radial tire in which a single-wire steel cord (type 2 cord) of the second embodiment is embedded.

15A is a cross-sectional view illustrating a single-wire steel cord of Comparative Example 1, and FIG. 15B is a schematic view illustrating a single-wire steel cord of Comparative Example 1. FIG.

16A is a cross-sectional view showing a single-wire steel cord of Comparative Example 2, and FIG. 16B is a schematic view showing a single-wire steel cord of Comparative Example 2. FIG.

FIG. 17 is a cross-sectional view showing each of the single-wire steel cords of the example and the comparative example for explaining the cord rigidity.

FIG. 18 is a perspective view showing a test piece used for a belt durability test.

FIG. 19 is a cross-sectional view of a test piece used for a belt durability test.

FIG. 20 is a schematic view showing a belt durability tester.

[Explanation of symbols]

2, 2A, 2B, 2C, 2D: single wire steel cord, 7: flattening machine (drive roll rolling device), 8: corrugating machine (pin roll processing device), 10A, 10B: tire, 12A, 12B, 14A, 14B ... Belt layer (tire belt layer),

Claims (20)

[Claims] 1. A single-wire steel cord comprising a single wire having two flat surfaces facing each other due to flattening of a round wire and two round curved surfaces facing each other. The flatness ratio D / W is in the range of 0.50 to 0.95, and is corrugated at least in the minor axis direction, and is used by being embedded in the tire belt portion so that one flat surface faces the tire tread surface side. A single-wire steel cord, characterized in that: 2. The single-wire steel cord according to claim 1, wherein the corrugation is crimping only in a short diameter direction. 3. The crimping process according to claim 1, wherein the corrugated height is set to 0.1.
3. The single-wire steel cord according to claim 2, wherein the length is in a range of from 0.05 to 0.3 mm. 4. The single-wire steel cord according to claim 1, wherein the corrugation is a crimping process performed in a short diameter direction and a long diameter direction, respectively. 5. In the crimping, the corrugated height in the minor axis direction is in a range of 0.05 to 0.3 mm, and the corrugated height in the major axis direction is in a range of 0.05 to 0.5 mm. The single-wire steel cord according to claim 4, characterized in that: 6. The aspect ratio D / W is set to 0.80 to 0.95.
The single-wire steel cord according to claim 4, wherein: 7. The corrugation, wherein the pitch interval is 2 to 20 m.
2. The single-wire steel cord according to claim 1, wherein the length is within a range of m. 8. The single-wire steel cord according to claim 1, wherein the corrugation is a pin roller process including only a smoothly continuous curved portion that does not include a linear portion in one plane. 9. The corrugation includes a combination of circular arcs, a sinusoidal curve, a continuous arc of a cycloid (spiral curve), a continuous arc of a cardioid (heart-shaped curve), and a continuous arc of a tratrix (suspended linear curve). The single-wire steel cord according to claim 8, wherein the single-wire steel cord is a smoothly continuous curve formed by combining one or two or more selected from the group consisting of: 10. The single-wire steel cord according to claim 8, wherein the corrugation is a pin roller processing of only a short diameter. 11. The single-wire steel cord according to claim 8, wherein the pin roller processing has a corrugated height in a range of 0.05 to 0.3 mm. 12. The single-wire steel cord according to claim 8, wherein the corrugation is performed by pin roller processing performed in a short diameter direction and a long diameter direction, respectively. 13. In the pin roller processing, the corrugated height in the minor diameter direction is in the range of 0.05 to 0.3 mm, and the corrugated height in the major diameter direction is in the range of 0.05 to 0.5 mm. The single-wire steel cord according to claim 12, characterized in that: 14. The aspect ratio D / W is set to 0.80 to 0.9.
13. The single-wire steel cord according to claim 12, wherein the value is in the range of 5. 15. The round wire has a weight of 280 to 450 kg.
single wire steel cord according to claim 1, characterized in that it has a tensile strength in the range of f / mm ^2. 16. The round wire may be 0.07 to 1.00.
2. The composition of claim 1, having a carbon content of about 1% by weight.
Single wire steel cord as described. 17. A method for producing a single-wire steel cord used by being embedded in a tire belt portion so that one flat surface faces a tire contact surface side, wherein (a) an aspect ratio of a minor axis D to a major axis W. A step of flattening the round wire so that D / W is in the range of 0.50 to 0.95, and (b) a step of corrugating the flat wire flattened in the step (a) in a minor axis direction. And a method for manufacturing a single-wire steel cord. 18. The method according to claim 17, wherein in the step (b), the flat wire is caulked or pin-rolled. 19. The method according to claim 19, further comprising, before the step (a), a long diameter corrugating step of corrugating the round wire in a direction orthogonal to the corrugating direction in the short diameter corrugating step (b). 18. The method of claim 17, wherein the method comprises: 20. The method according to claim 18, wherein in step (a), the aspect ratio D / W is in the range of 0.80 to 0.95.